Program: GN-2005A-Q-10

The discovery that most nearby massive spheroids harbour a black hole of proportionate mass means that the co-evolution of spheroids and black holes is now recognised as one of the key areas in observational cosmology. At high redshifts quasars and their hosts provide a unique window on this evolution, as the only class of object in which both galaxy and black-hole properties can be directly measured. Using NICMOS on HST we have discovered evidence that the hosts of quasars at z=2 are already massive, luminous galaxies, and in Semesters 2004A&B we have begun to use Gemini+NIRI to extend this study through the crucial cosmic epoch z=2-4. Here we propose to complete the quasar sample begun in 2004A. This project exploits the capabilities of Gemini+NIRI to the full, as we require both excellent image quality and the ability (impossible with NICMOS) to detect low-surface brightness emission at K.